Jon R
Senior Member
I suspect many of you more experienced folks will read this and say, "no s%#t, Sherlock," but I thought I'd post anyway.
I've been using my new system for about 6 weeks now. I have two 200 watt rigid Renogy panels with a Victron MPPT 100/30, and 200Ah of LiFePO battery. I chose the panels to maximize my use of the area between the roof vents on the Grandby, and my thought was that, while it's way more panel than I need in sunny weather, it would make a big difference the dark cloudy off season in the PNW.
After experiencing a few completely cloudy days in the Seattle area, including yesterday and today, which are among the longest days of the year, I wonder if I should have bothered with the second panel. If it's sunny or even partly sunny, my system is caught up to fully charged by mid to late morning. If it's heavy overcast (even now in July), I get about 5 to 7% of rated panel output. This helps offset the refrigerator draw so I don't fall much further behind during the middle of the day, but it doesn't get the battery ahead at all.
So my hope that doubling the panel capacity, relative to what would be needed for indefinite sunny weather use, would make a significant difference in PNW overcast does not appear to be playing out. Maybe it will make the difference in some partial sun campsite conditions in sunny weather. I can see in the gray season on longer trips I will be largely dependent on the DC to DC charger, but at least my large battery will give me 3 to 4 days before I must charge.
So if I was doing this again, I would go with the advice several of you have previously given to get one panel of the largest power rating that fits and is compatible (currently 300 or 320 watts probably), save the extra weight on the roof, and call it good.
I've been using my new system for about 6 weeks now. I have two 200 watt rigid Renogy panels with a Victron MPPT 100/30, and 200Ah of LiFePO battery. I chose the panels to maximize my use of the area between the roof vents on the Grandby, and my thought was that, while it's way more panel than I need in sunny weather, it would make a big difference the dark cloudy off season in the PNW.
After experiencing a few completely cloudy days in the Seattle area, including yesterday and today, which are among the longest days of the year, I wonder if I should have bothered with the second panel. If it's sunny or even partly sunny, my system is caught up to fully charged by mid to late morning. If it's heavy overcast (even now in July), I get about 5 to 7% of rated panel output. This helps offset the refrigerator draw so I don't fall much further behind during the middle of the day, but it doesn't get the battery ahead at all.
So my hope that doubling the panel capacity, relative to what would be needed for indefinite sunny weather use, would make a significant difference in PNW overcast does not appear to be playing out. Maybe it will make the difference in some partial sun campsite conditions in sunny weather. I can see in the gray season on longer trips I will be largely dependent on the DC to DC charger, but at least my large battery will give me 3 to 4 days before I must charge.
So if I was doing this again, I would go with the advice several of you have previously given to get one panel of the largest power rating that fits and is compatible (currently 300 or 320 watts probably), save the extra weight on the roof, and call it good.